1. Field of the Invention
The invention relates to a shaft packing with a casing between whose legs is clamped a disk-like packing member having one disk forming a protective lip and the other disk a packing lip, the internal diameter of the disks in the unfitted state of the shaft packing being smaller than the external diameter of the shaft to be packed or sealed and an expanding ring is positioned between the disks.
2. Description of Prior Developments
In the case of DE 3,601,349 A1 an expanding ring is made from an elastomer and in the case of U.S. Pat. No. 3,250,541 the expanding ring is a metal part.
A similar shaft packing is also known from DE 3,927,458 A1 , in which a disk-like packing member having a packing lip is formed by a conical, polymeric material disk constructed in the manner of a cup spring. The disk is provided radially from the inside with a slit, so that in the unfitted state a protective lip and a packing lip are formed, whose packing edges engage on one another. The arrangement is such that the diameter of the packing edges in the unfitted state of the shaft packing corresponds to the shaft diameter of the shaft to be packed. The slit is made in the disk under an angle such that the wall thickness of the protective lip increases radially outwards and that of the packing lip radially inwards.
On pressing onto the shaft, the packing lip is inverted in the direction counter to the overall inclination of the packing disk with respect to the shaft axis in such a way that the packing lip presses elastically radially inwards onto the shaft circumference and consequently brings about the desired packing solely as a result of its intrinsic elasticity without using a worm spring such as is conventionally used with shaft packings.
However, the above-described construction suffers from the following disadvantages. Producing the slit radially from the inside is complicated, particularly in connection with the necessary precision of the angular position relative to the axis. With regards to the tolerances of the shaft and the packing disk it is difficult to orient the packing edges of the protective lip and the packing lip precisely to the external diameter of the shaft to be packed. This is necessary in the known construction, because if there is the slightest radial overlap of the particular packing edge and the shaft diameter it is no longer possible to fit the packing. It must then be expected that both the protective lip and the packing lip will invert in the same direction, which does not permit the necessary packing or sealing action.
The problem of the invention is to so construct a shaft packing of the described type, that the indicated disadvantages are avoided and a simple manufacture and fitting are ensured without any risk of inverting the protective lip or packing lip in the same direction and at the same time always guaranteeing a reproducible, good packing or sealing action.